Fan blade

Abstract: A fan blade comprising a body (10) having a tip end (20) and an in-board end (18) is configured with first (26) and second (28) fin portions that extend along the trailing edge (16) of the body (10) of the van blade. The first fin portion (26) extends from the in-board end (18) of the fan blade along the trailing edge (16) toward the tip end (20), while the second fin portion (28) extends from the tip end (20) of the van blade along the trailing edge (16) toward the in-board end (18). Both the first (26) and second (28) fin portions extend outwardly from the trailing edge (16) of the body at an angle to the trailing edge (16). A slot (30) or gap exists between the first (26) and second (28) fin portions and each such fin portion has a tapered width which narrows in the direction of the tip end (20). The width of the first fin portion (26) is greater than the width of the second fin portion (28) and the two fin portions may or may not be co-planar in order to optimize air flow.

Description: The invention relates to fan blades. It is known that a blade having a "twist" thereto provides more lift (and hence an increase in the displacement of air) than blades which are not so "twisted" or are uniform and consistent along their length. The most economical manner to produce aluminum fan blades is by the extrusion process, however, the extrusion process generally only produces non-twisted blades. To impart a uniform angular twist in an extruded airfoil requires mechanically yielding the airfoil in a secondary process. This secondary process is costly and it often produces inconsistent results. Consequently, it is desirable to combine the performance of the "twisted" blades with the economics of the uniform blades to achieve a high performance blade at a relatively low cost. One attempt to achieve this result is disclosed in Patent Specification US-A-4 618 313 which discloses an axial propeller blade comprising a single tab secured along its trailing edge. This single tab is also disclosed as being inclined from the blade at an angle of from 10° to 70° so as to enhance the lift of the blade. However, the tab is planar and of uniform or consistent configuration. Consequently, there is no possibility of this tab having one configuration and/or angle at the root end of the blade and another configuration and/or angle at the tip end of the blade so as to be more consistent with "twisted" blades. There is also no likelihood of this tab conforming to the multiple planes normally found in "twisted" fan blades which cause or result in increased performance. Patent Specification FR-A-991 183 discloses a fan blade having flaps or tabs articulated at the trailing edge thereof effectively to give the fan blade overall a twist. According to the invention there is provided a fan blade comprising: (a) a body having a tip and an end opposite the tip, the body also having a leading edge and a trailing edge between the tip and the end; and (b) multiple fin means coupled to the trailing edge of the body to direct air flow across the body, the fin means comprising at least two fin portions with a first fin portion extending at a first angle outwardly from the trailing edge along a first length of the fan blade and a second fin portion extending at a second angle outwardly from the trailing edge along a second length of the fan blade; characterised in that the first and second fin portions are formed by extrusion with the body of the fan blade. Such a fan blade thus incorporates a trailing fin the angle of which can vary along the length of the fan blade and which can be more economical to construct than a "twisted" fan blade. It can however have an operating performance which is comparable with or exceeds that of a "twisted" fan blade. The multiple fin means which is extruded at the trailing edge of the body preferably comprises an end fin extending from an in-board end of the fan blade and a tip fin extending inwardly from the tip of the fan blade toward the in-board end. Advantageously the end fin and the tip fin are spaced a distance from each other and are in alignment on the trailing edge of the body of the fan blade. Furthermore, the end fin and the tip fin both have a narrowing or a tapered width with the width of the end fin being greater than the width of the tip fin. The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which: Figure 1 is a perspective view of a fan blade according to the invention including a fin extruded at the trailing edge of the blade; Figure 2 is a sectional view taken on line 2-2 of Figure 1 illustrating the in-board portion of the fin pitched at a greater angle with respect to the blade than the out-board portion of the fin; and Figure 3 is a front view of a fan blade according to the invention illustrating a configuration wherein both fin portions are in alignment with each other. Figures 1 to 3 illustrate a fan blade 10 comprising a body 12 having a leading edge 14 and a trailing edge 16. The body 12 has an in-board or root end 18 and an out-board or tip end 20 directly opposite the in-board end 18. The in-board end 18 is secured to a propeller or the like through the use of mounting means such as a shaft 22 mounted to the in-board end 18. The fan blade 10 is configured with a two-piece fin 24 which is extruded with the body 12 of the fan blade 10. However, in other embodiments, the fin 24 may comprise more than two pieces if required for performance optimization. As shown in this two-piece fin embodiment, a first fin portion 26 extends outwardly from the trailing edge 16 and extends from the in-board end 18 along a portion of the trailing edge 16 towards the tip end 20 of the body 12. A corresponding second fin portion 28 extends inwardly from the tip end 20 of the body 12 along the trailing edge 16 towards the in-board end 18. The fin portions 26 and 28 can extend within the same plane and be linearly aligned with each other if desired (see Figure 3). However, as illustrated in Figure 2, it is possible for the fin portions 26 and 28 to be independently aligned, or be non-linear, and they also need not extend within the same plane. Between the fin portions 26 and 28 is a slot 30 which forms an obtuse angle with respect to the trailing edge 16. As a result of this configuration, the first fin portion 26 is trapezoid in shape while the second fin portion 28 comprises an obtuse triangle. In other embodiments, there may be three or more fin portions along the body 12 with each such portion located and aligned as needed to maximize air flow across the blade 10 . The fan blade 10 with the fin portions 26 and 28 can be made of aluminum, other metal, alloy or plastics. Figure 2 illustrates how the fin portions 26 and 28 can be pitched at optimum angles to maximize air flow on the in-board end 18. In this case, the in-board fin portion 26 is pitched at a higher angle than the out-board fin portion 28. Typically, the lower angular velocity present on axial fans near the centre of the fan ( ie in-board region) requires greater blade twist in that area to provide airflow which is uniform with or similar to that generated by the out-board portion of the blade 10.

Claims: A fan blade comprising: (a) a body (10) having a tip (20) and an end (18) opposite the tip (20), the body (10) also having a leading edge (14) and a trailing edge (16) between the tip (20) and the end (18); and (b) multiple fin means (26, 28) coupled to the trailing edge (16) of the body (10) to direct air flow across the body (10), the fin means comprising at least two fin portions with a first fin portion (26) extending at a first angle outwardly from the trailing edge (16) along a first length of the fan blade and a second fin portion (28) extending at a second angle outwardly from the trailing edge (16) along a second length of the fan blade; characterised in that the first and second fin portions (26, 28) are formed by extrusion with the body (10) of the fan blade. A fan blade according to claim 1, wherein the first (26) and second (28) fin portions are separated from each other by an open slot (30). A fan blade according to claim 1 or claim 2, wherein the first fin (26) portion extends from the end (18) of the body (10) to a first position on the trailing edge (16) of the body (10). A fan blade according to any one of claims 1 to 3, wherein the second fin portion (28) extends from the tip (20) of the body (10) to a second position on the trailing edge (16) of the body (10). A fan blade according to claim 4, wherein the first fin portion (26) is configured as a trapezoid. A fan blade according to claim 5, wherein the second fin portion (28) is configured as an obtuse triangle. A fan blade according to claim 6, wherein the first and second fin portions (26, 28) have a tapered width which narrows in the direction of the tip (20). A fan blade according to claim 7, wherein the tapered width of the first fin portion (26) is larger than the tapered width of the second fin portion (28). A fan blade according to claim 8, wherein the first and second angles are not equal. A fan blade according to claim 8, wherein the first (26) and second (28) fin portions are linearly aligned. A fan blade according to claim 8, wherein the first (26) and second (28) fin portions are not linearly aligned. A fan blade according to claim 8, wherein the first (26) and second (28) fin portions are planar. A fan blade according to claim 8, wherein the first (26) and second (28) fin portions are non-planar. A fan blade according to any one of claims 1 to 13, wherein the first and second fin portions (26,28) are pitched at different angles to one another. A fan blade according to any one of claims 1 to 13, wherein the in-board fin portion (26) is pitched at a higher angle than the outboard fin portion (28).

Inventors: MONROE ROBERT C, MONROE, ROBERT C.
Applicants: HUDSON PRODUCTS CORP, HUDSON PRODUCTS CORPORATION
Application year: 1994
Main classification: F04D29
IPC codes: F04D29, B21C23, B64C11